Epigenetics refers to heritable changes in gene expression in the absence of alterations in the DNA sequence (Russo et al., eds. (1996) Epigenetic Mechanisms of Gene Regulation. Woodbury, N.Y.: Cold Spring Harb. Lab. Press). Epigenetic modifications are thought to be one of the critical mechanisms that mediate gene-environment interactions and play a major role in tissue- and cell-type-specific differences in gene expression (Razin & Riggs (1980) Science 210:604-10; Zuckerkandl (1974) Biochimie 56:937-54) and many other cellular processes (Liu et al. (2013) Front. Genet. 4:182; Wolffe & Matzke (1999) Science 286:481-86; Zentner & Henikoff (2013) Nat. Struct. Mol. Biol. 20:259-66). The role of epigenetics in disease is well established in the field of cancer (Baylin & Jones (2011) Nat. Rev. Cancer 11:726-34; Feinberg (2007) Nature 447:433-40) and imprinting disorders (Barlow (2011). Annu. Rev. Genet. 45:379-403).
There are many FDA-approved medications, some with longstanding clinical use, that influence epigenetic modifications in addition to their originally established functions. An example is the anti-epileptic agent valproic acid, which was recently shown to be a potent histone deacetylase inhibitor (HDACi; Phiel et al. (2001) J. Biol. Chem. 276:36734-41). Several widely-used supplements or dietary substances, such as folic acid, genestein, and curcumin, are known to influence epigenetic modifications (Meeran et al. (2010) Clin. Epigenetics. 1:101-116).